Mainly fixing some bugs from the userspace application.
Details:
- Added validations for duplicate IPv4 pool and session insertions.
- I also realized that the IPv4 pool's design was somewhat suboptimal and refactored it (an error code died in the process).
- Fixed a unit test from translate the packet, which was using unallocated memory.
- Dropped several command line arguments of functionality not yet implemented, to prevent some confusion.